Blood Collection Tubes

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Blood Collection Tubes

Most blood collection tubes contain an additive that either accelerates clotting of the blood (clot activator) or prevents the blood from clotting (anticoagulant). A tube that contains a clot activator will produce a serum sample when the blood is separated by centrifugation and a tube that contains an anticoagulant will produce a plasma sample after centrifugation. Some tests require the use of serum, some require plasma, and other tests require anticoagulated whole blood (Table 1).
Table 1. The most commonly used blood collection tubes.
Tube cap colorAdditiveFunction of AdditiveCommon laboratory tests
Light-blue
3.2% Sodium citratePrevents blood from clotting by binding calciumCoagulation
Red or gold (mottled or "tiger" top used with some tubes)
Serum tube with or without clot activator or gelClot activator promotes blood clotting with glass or silica particles. Gel separates serum from cells.Chemistry, serology, immunology
Green
Sodium or lithium heparin with or without gelPrevents clotting by inhibiting thrombin and thromboplastinStat and routine chemistry
Lavender or pink
Potassium EDTAPrevents clotting by binding calciumHematology and blood bank
Gray
Sodium fluoride, and sodium or potassium oxalateFluoride inhibits glycolysis, and oxalate prevents clotting by precipitating calcium. Glucose (especially when testing will be delayed), blood alcohol, lactic acid